A-D-Xylofuranose

O-isopropylidene-a-D-xylofuranose (CsHijO, 20037-27-4) see Stavudine isopropyl iodide... 

Many polyhydroxylated quinolizidines <1995CRV1677>, frequently designed as azasugars, are powerful glycosidase inhibitors and therefore have potential therapeutic application. The 7-oxa-l-azabicyclo[2.2.1]heptane derivative 191, obtained from 3-0-benzyl-l,2-0-isopropylidene-l,5-pentadialdo-a-D-xylofuranose with... 

For the cw-dihydroxylation of protected lL-l,2 3,4-di-0-isopropylidenecyclohex-5-ene-l,2,3,4-tetrol (22g) to the diol lD-l,2 3,4-di-0-isopropylidene-a/to-inositol by RuClj/aq. Na(IO )/EtOAc-CH3CN/0°C cf. 3.1.2.1 and Fig. 3.3 [347]. Oxygen insertion by stoich. RuO /CCl occurred in addition to the secondary alcohol oxidation of the five-membered ring 5-0-benzoyl-l,2-0-isopropylidene-a-D-xylofnranose, giving the six-membered ring l,2-0-isopropylidene-6-0-benzoyl-3-oxa-a-D-e/7fftro -4-hexulopyranose-a-D-xylofuranose [325]. 

Sugars containing a carbon-phosphorus bond have been prepared by application of the Michaelis-Arbuzov reaction to bromodeoxy sugars. Thus, the reaction of 5-bromo-5-deoxy-l,2-0-isopropylidene-3-O-methyl-a-D-xylofuranose (131) with triethyl phosphite yields the corresponding diethyl phosphonate (132) compound 132 was employed for the synthesis of a sugar derivative having phosphorus as... 

Carbohydrate oxetanes have been prepared from deoxyiodo sugars without die use of strongly alkaline reagents. Thus, treatment of 5-deoxy-5-iodo-l,2-0-isopropylidene-a-D-xylofuranose with silver fluoride in cold pyridine afforded 3,5-anhydro-l,2-0-isopropylidene-... 

Apparently related to the two preceding reactions is the action of 2% methanolic hydrogen chloride on l,2-0-isopropylidene-5-seleno-a-D-xylofuranose (72) (obtained from the benzylseleno derivative, 71), which affords83 a mixture of 2,5-anhydro-5-seleno-D-xylose (and -D-lyxose) dimethyl acetal (73). Similarly, the action of the same reagent... 

Uryu and coworkers also reported the first synthesis of a nonhydro-lyzable polysaccharide by cationic, ring-opening polymerization of an oxetane ring. The monomer was 3,5-anhydro-l,2-0-isopropylidene-a-D-xylofuranose, and it formed a polymer of molecular weight of 10,000-11,000. Spectral and optical data indicated regular polymerization to a (3— 5)-linked polymer of 1,2-O-isopropylidene-a-D-xylofuranose.14... 

Deamination performed in hydrochloric acid solution may result in the formation of chlorine-containing products, as illustrated by the deamination of 5-amino-5-deoxy-l,2-0-isopropylidene-a-D-xylo-furanose, which gave the 5-chloro-5-deoxy derivative (isolated in 6% yield).49 1,2-O-Isopropylidene-a-D-xylofuranose, the major prod-... 

Similarly, the Michaelis-Arbuzov reaction of the 5-bromo-3-0-methyl compound 8 with diethyl ethylphosphonite at 130-150° resulted29 in a quantitative yield of 5-deoxy-5-C-[(RS)-(ethoxy)ethylphos-phinyl]-1,2-0-isopropylidene-3-O-methyl-a-D-xylofuranose, which,... 

Compound 41 was obtained almost quantitatively by heating 42 in diethyl butylphosphonite, which provides, at least partly, the complicated reason for the lower yields from the Michaelis - Arbuzov reaction of 5-halogeno-l,2-0-isopropylidene-a-D-xylofuranose where the hydroxyl group on C-3 was not protected (see earlier). 

The preparation of 1,2-O-cyclohexylidene-a-D-xylofuranose (22) (Expt 5.117) from 1,2-O-cyclohexylidene-a-D-glucofuranose illustrates the use of sodium metaperiodate for the cleavage of carbon-carbon bonds in a-diols (see also Section 4.2.55, p. 454). In this case C-6 is lost as formaldehyde and C-5 is converted into an aldehyde group. This aldehydic product is isolated as a dimer, which is then reduced in methanol solution with sodium borohydride to the xylofuranose derivative (22). 

Among them, the first compound prepared and studied was 3,5-anhydro-1,2-0-isopropylidene-a-D-xylofuranose (87)347 349 and its 1,2-O-cyclohexy-lidene analogue.350 Formation of the oxetane ring is based on the internal substitution of an conventional leaving group X at C-5, or surprisingly, also phthalimido group in 86 351 for application of the Mitsunobu reaction, see Ref. 349. 

Platinum-catalyzed oxidation of D-glucitol affords L-gulose and D-glucose. The specificity of this reaction is probably due to both statistical and steric factors. A related example is the conversion of L-sorbose into L-vy/o-2-hexulosonic acid in 62% yield (see Ref. 1, p. 1129). Similar oxidation of 1,2-acetals of a-D-glucofuranose and a-D-xylofuranose affords the respective glycuronic acids whereas, under more drastic conditions, the former acetal is converted into 1,2-O-isopropylidene-o -D-vy/o-hexofuranos-5-ulosono-6,3-lactone, a synthetic precursor of ascorbic acids. 

Reduction of 3-O-benzyl-1,2-O-isopropylidene-a-D-xylo-pento-dialdo-l,4-furanose (23) with lithium aluminum deuteride, followed by catalytic debenzylation, gave an unequal R and S mixture (24) of 1,2-O-isopropylidene-a-D-xylofuranoses-S-d that was converted into a mixture (25) of tetra-0-acetyl-/3-D-xylopyranose-(R)- and (S)-5-d. Inspection of the p.m.r. spectrum showed, for the C-5 proton, two signals that were doublets, with splittings of 4.2 and 8.1 Hz, corresponding to a,e and a,a coupling, respectively, with the axial proton at C-4. 

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